Semiconductor processing systems having processing devices are widely used in modem products, such as automobiles, cell phones, kitchen appliances, and video gaming devices, etc. to perform a variety of complex functions. For instance, programmable devices, such as microcontrollers, field programmable gate array (FPGA), and programmable logic devices (PLDs), are commonly used to provide this variety in an economical manner.
Conventionally, designing a processing system using a general-purpose processing device typically involves a programmer familiar with both the application or product in which the processing system is to be used, and the capacity and limitations of the processing system. In general, the design sequence involves determining the requirements of the application, programming a solution using the processing device based upon what is known of the system's requirements, and adding to, deleting from, or completely re-writing processing device code (also referred to as embedded firmware) for the processing device as the system requirements change. Thus, many typical implementations, which begin simply with an ‘if-then-else’ code statement, or a case structure, generally grow organically to an unwieldy, hard-to-understand, hard-to-verify, and unmaintainable implementation.
For example, one commonly used technique for defining or mapping output behavior for a processing system uses truth tables. However, there are many possible firmware implementations of a truth table, depending upon a programmer's skills in framing the system problem as well as technical coding skills.
Yet another problem in designing or configuring processing systems arises from the need to convert variable and continuous input signals to a number of discrete values, each having one or more setpoints or threshold values and select hysteresis associated therewith. In a typical sensing and control system, input devices usually produce a continuous range of values, but the system has to act discretely, or operate in one of a discrete set of states. Furthermore, the required hysteresis has to be explicitly specified and treated as additional thresholds. According to one conventional approach to convert an input from continuous to discrete, a user first selects the actual threshold values and hysteresis required for a particular continuous input (such as writing down or capturing the continuous input). Then the user writes embedded firmware to choose an input and to compare the chosen input to one or more thresholds, applying hysteresis as defined.
Moreover, to change the values of the thresholds, the user has to update elements of the embedded firmware (e.g., constants, variables). Alternatively, a communication interface and/or protocol with more firmware is employed to interpret commands and modify thresholds.